Torrey Squirrels

Question: Can the Eastern gray squirrel (Sciurus carolinensis) be employed in the assisted migration of Torreya taxifolia? 

Historically, Torreya Guardians have been wary of seed predation on Florida torreya by the gray squirrel because of their appetite for its large seeds. However, my brief literature review indicates that the gray squirrel may be useful to Guardians, as this rodent is known to distribute significant numbers of the large seeds of torreyas and other species into microhabitats conducive to torreya establishment, bury seeds to suitable germination depths, cull seeds containing seed-predator insects & other debilitating factors, and occurs within a suitable geographical range. Therefore, I have assembled the information below so that Torreya Guardians can take a closer look at the roles that the gray squirrel might provide in (1) enlarging the geographic range of the Florida torreya northward of the presumed range of the torreya pathogen and (2) significantly increasing the torreya populations within that enlarged range.

Torreya Guardians already know that the Eastern gray Squirrel can affect our assisted migration tactics. This rodent (1) raids mother trees of their seeds, (2) steals potted seeds, and (3) caches seeds in developed areas and wildlands that can germinate and grow into naturally occurring individuals and colonies. Although we know this third thing, and we are happy about it when new seedlings “volunteer,” we have historically focused on the first two annoyances. In my view, this is because our historical charge has been to propagate and migrate, and obviously, we cannot increase the population until we learn how to propagate and nurture it. I believe we have now done those two things well enough to start looking at natural colonization strategies.

Being a wildlife biologist who sees mammals as the natural dispersers of Florida torreyas – not wind or water or birds – I suggest that wildlife biologists assess the potential for expanding (1) colony sizes of existing artificially planted trees, (2) leapfrog colonizations near existing artificial individuals and colonies, and (3) large-scale colonizations within national and state forestlands. However, as Daniel Boone exhorted, we must be sure we are right before we go ahead. My literature research indicates that there is only one good candidate for spreading the Florida torreya in the Eastern U.S., and that is the Eastern gray squirrel. Ergo, I have focused below only on that species.

The gray squirrel forages for, among other things, the relatively large seeds (= fruits, nuts) of trees such as the walnut (Juglans nigra), hickories (Carya spp.), oaks (Quercus spp.), and chestnuts & chinkapins (Castanea spp.). Chestnut trees historically were particularly reliant on gray squirrels, but the pines, beech, hazel, and oaks also benefit greatly, and so probably does the Florida torreya.

Foraged seeds that contain seed-predator insects are eaten immediately, whereas pristine seeds are stored for later consumption, especially as winter food. Seeds are stored individually via burial to depths of at least one inch, one source claiming below the frost line. Seeds may also be deliberately cracked before burial, it is said to prevent germination. Seeds are generally stored relatively closely to the finding gray squirrel’s nest tree, but can also be dispersed over an area of up to seven acres. One study revealed that gray squirrels can re-find up to two-thirds of the nuts they buried.

Gray squirrels employ a mnemonic storage technique called “spatial chunking” (also seen in rats), where seeds are sorted and buried according to size, type, and possibly taste and food value. By spatial chunking, zoologists mean that, for instance, hickory nuts will be buried in one area and oak acorns in a separate place. It has also been found that gray squirrels store preferred seeds in wide open spaces, possibly to increase a robber’s risk of predation when randomly foraging away from cover. Presumably, the storing squirrel experiences less risk because it knows where its seeds are buried, can go directly to them, and thus be less jeopardized by predators.

Another way that gray squirrels try to prevent neighboring squirrels from stealing their stores is the tactic of “deceptive caching;” that is, they only pretend to bury a nut, especially if they see another squirrel watching them.

Gray squirrels immediately consume insects they serendipitously find imbedded within seeds. Furthermore, while nest-caching squirrel species store pristine and insect-containing seeds together and thus increase seed-feeding insect populations, the gray squirrel’s habit of storing only pristine seeds and storing them separately acts to limit seed-predator insects. This practice could also limit seed-fungi infestations, which is another potential subject for research.

Gray squirrels are important in forest regeneration, much more so than other North American squirrel species. Of all the North American squirrel species, only the gray squirrel stores most of its hoard in individual caches scattered over a wide area in locations that include those that do not already have forest tree cover. Studies show that gray squirrels bury 97% of the seeds they find and immediately eat only the 3% that contain insects. Studies show widely variable rates of gray squirrels’ re-finding their caches, one being 70% and another only 36%. The remaining seeds were eaten by other animals (one study lists 20%) and only 10% germinating. Nevertheless, those that do germinate are likely to be the ones furthest from the nest tree and thus naturally disseminated. The net effect of planting so many healthy & insect-free seeds is that vigorous & genetically superior trees are selected for in the forest regeneration process.

Other North American species of squirrels tend to use nest caches. For example, the red squirrel (Tamiasciurus hudsonicus) stores most of its seeds in tree cavities and buries only 11% of them. Seeds stored in tree cavities will not germinate nor aid in forest regeneration. The red squirrel is thus considered a seed predator and not a forest regenerator.

Similarly, the Indochinese flying squirrels (Hylopetes phayrei) and particolored flying squirrel (Hylopetes alboniger) in southern China’s rain forests chew two grooves in the shells of smooth, egg-shaped or rounded nuts to wedge them firmly between branch crotches. The grooves hold the nut between the branches much like a sturdy mortise-tenon joint that carpenters use to attach legs onto furniture. They choose smaller saplings, placing caches roughly 2 m above the ground and 10-25 m from the nearest nut-producing tree. This makes sense in their humid environment, as a seed stored in the ground or dead log would rapidly either rot or germinate, and a seed falling out of a tree crotch would be quickly found and eaten by other herbivores. Thus, these two squirrel species are also seed predators.

Answer: Gray squirrels are expected to disperse the Florida torrey regardless of our intentions, so plant one and just stand back!

The Vertical Forest

The Hanging Gardens of Babylon are famous, although no one knows where they were physically located. There is even some doubt whether this garden ever actually existed, as it was only the Babylonian priest Berossus who wrote in 290 BCE from first-hand (?) sightings. Regardless, so many of us want it to be true, and try to make it true of our own ‘castles,’ even if only in small part. 

I have mixed feelings about it. I love plants. Plants are gods, replacing wastes with the vapors and substances needed by the living. We keep small plants indoors for their ambiance, and larger perennials in landscaping features to hide rude concrete and steel and to provide for wildlife. But we fear large trees next to our houses and paved driveways, and are right to eschew them. Only shrubs and small tree species are allowed within falling-limb and pavement-buckling distance of most abodes. But mirages of hanging gardens still sway in the whims of my daydreaming mind.

An Italian architect named Stefano Boeri and his staff designed two residential towers in Milan, Italy, called Il Bosco Verticale, or The Vertical Forest. At 80 m and 112 m in height, they host appx 20,000 plants in balcony containers. This greenery is comprised of perennial herbaceous flowers, shrubs, and small and medium-sized trees. I think it also includes lianas, but that is not stated in media articles. The two towers are sweet, if not exactly lush. For example, the greenery is in spots rather than sweeps and washes, as it appears that nothing is allowed to grow on exterior walls. Furthermore, gardener pruning keeps plants well separated.

https://www.cnn.com/style/article/riba-vertical-forest-stefano-boeri/index.html

The carbon footprint of the spectacle has been assessed, concluding that it would take many decades for its flora to offset construction impacts and maintenance costs. This is in large part due to the additional structural needs for supporting the heavy weight of the plants and their containers, potting media, and water. In addition, the large balconies, being appx 40% of the total floor space, are quite heavy.

Another limit on the carbon footprint offset is the need for three gardeners working nearly year-round to clip the flora. Firstly, most plants really do not need to be clipped. Secondly, this keeps exterior walls possibly overly exposed to the elements. Thirdly, gardeners are expensive. Are three gardeners working nearly year-round really necessary? For example, one video depicts gardeners pruning low-growing flowering plants even though most perennial cultivars exhibit self-limiting growth simply by dying back in the winter. Planting small and medium-sized trees also appears to be a mistake, both because of their weight and the need for artificial irrigation and pruning. Shrubs grow plenty large on balconies, and annual pruning easily ensures that they do not grow too heavy.

The videos and articles I have seen do not mention how the plants get watered. Watering can be done automatically with drip irrigation systems, or by shunting rainwater into plant containers, or by choosing drought-tolerant cultivars that are fine when watered only when it rains. Too, water is heavy, so keeping plants small and maintaining only relatively small plant containers reduces the load on and size of such balconies.

Thus, the building’s carbon footprint can be reduced substantially by growing smaller, more drought-tolerant plants in smaller containers on smaller balconies.

Another weakness of the Milan Vertical Forest is the value placed on the amenity that the vegetated balconies were supposed to offer residents. The architect doubtless envisioned residents having breakfast and dinner there, relaxing outdoors with a good book, or perhaps having a smoke while enjoying the scenery. However, Milan’s climate is evidently too chilly for most of the year, so residents remain nearly entirely indoors when home. Conversely, some cities are simply too hot for hanging out outside during summer.

After I ran across and enjoyed several Vertical Forest articles and videos, several people coincidentally posted articles on it on Facebook. A bunch of sharks on one site piled on the idea in a virtual feeding frenzy, falling all over themselves to pan the idea. It never ceases to amaze me that invention is literally always attacked by those who are unable to understand that prototypes are deliberately designed to find their own flaws so that future editions can be informed and become better. You can see some of that in the above text where I mention how some of the invention’s flaws can be easily mitigated. So, I decided to review the cartilaginous fish attacks to see if they had come up with any issues that I could not think of potential solutions for off the top of my head. Here goes:

AM: “Structure engineer had their math cut out on this project…”

Buford: Hmm, what does this comment mean, anyway?

 

WS: “I can only imagine the insect problem in this building.”

Buford: Why would the “insect problem” be any different in this building than in any other city building? For one thing, if this building were plopped down anywhere that I have ever lived, it would have many birds and lizards consuming the insects. Whatever, there are more plants around my single-story house than there are on the balcony of any of the vertical forest’s apartments. Dumb.

 

MO: “When good intentions go bad..roots verses concrete.. good luck if you’re living in that.”

Buford: Roots are not a problem in the proper plant containers. Duh.

 

AR: “It may work if it was designed for that purpose the roots may be controllable with the hydroponic system however all that being said moisture and concrete are not long term friends…”

Buford: Hydroponic systems are heavy and would have large labor costs in a vertical apartment forest. FYI, concrete and moisture are actually lovers – concrete continues to set long after you think it is dry. Indeed, concrete sets better underwater than under air. And anyway, if moisture were such a problem with buildings, then why is it so popular as a construction material all over the world? Do your due diligence.

 

PM: “…the cyclic loading from winds going through the trees couldn't possibly have been accounted for.”

Buford: This comment cracks me up. LOOK at the picture! In the first place, there is no more windage with than without the veggies. Secondly, PM is evidently not really aware of just how thorough professional architects are. THEY do THEIR due diligence.

 

WL: “In fact it might not even be possible to safely construct and operate such a building. The water it would require would be terribly heavy and difficult to manage.”

Buford: In fact, it was indeed safely constructed and is currently being safely operated because it was designed by architects who did their homework, and it was permitted by professionals who did their due diligence, too.

 

MEW: “This cannot be a good thing.”

Buford: What cannot be a good thing? We cannot read your mind.

 

MMB: “Well, you also need to look at the long term side effects...”

Buford: What long-term side effects? Oh, and can MMB possibly imagine that one of the purposes of prototypes is to “look at long-term side effects?”

 

BKB: “…it wouldn't last one windstorm in Alaska…”

Buford: This comment cracks me up. BKB apparently thinks something like this might even be designed for an Arctic or Antarctic locale (!); or that it is not a good idea for Miami or Houston because it wouldn’t be a good idea in Alaska, or something…

You get the picture. These people haven’t a clue about architecture, irrigation, plants, insects, birds, concrete, windage, logic, grammar… My suggestion to the OP of the thread is to delete asinine comments and Block dummies. That is what I do on my FB page. That way, thoughtful, informed, educated, progressive people could share reasonable information.

 

Pipsissewa Wilting

After building my house and moving into it, it seemed worthwhile to rent the adjacent pad where I lived in an RV travel trailer during the construction process. I signed up with hosting platforms Airbnb and Hipcamp, prepared site profiles, and then stood back, poured myself a cup of French roast, and waited for new friendships and income to roll in.

Both hosting platforms provide extensive and helpful instructions and advice to new hosts like myself. I was particularly impressed with the ability for prospective tenants to review host sites within standardized formats for ready comparisons. There also are provisions for hosts to provide additional information that does not fit into their standard forms’ boxes, and there are several ways that hosts can get further advice on setting up profile webpages; e.g., phone the platforms and talk to real humans, peruse competitor site profiles as examples, and join Facebook sites where hosts can advise each other.

One piece of advice that I took to heart was to put into my site profile how tenants could deal with any issues particular to my site. Consumers deserve fair warnings before plunking down their bucks. One fair warning I gave was about my driveway. I pointed out it was steep, and in the beginning surfaced with loose gravel that would make it difficult or impossible for small front-wheel-drive (FWD) cars to ascend.

There were two warnings that could have been added, but I was not experienced enough to know about them. One was that self-contained RVs or trailer towing vehicles must have strong engines due to the steep driveway, and the second was that self-contained and trailer-towed RVs both must be limited in length due to tight quarters. But I had no idea how powerful their engines needed to be or what maximum RV lengths can be accommodated on my site. So, what were my options in trying to determine these things? I could (1) get experience over time – good, bad, and ugly; (2) ask competitors for advice (right!); (3) seek guidance from RV consultants (but just try to find one in the yellow pages); and (4) ask the hosting platform companies (but they do not make site inspections). The last three took me back to alternative #1, so I hoped that experienced RV owners would know what their engines were capable of and how to shoehorn their RVs into tight slips. I knew those things when I lived in an RV.

The first tenants to arrive were able to drive their RV up to the site; however, they had to park their small FWD car down the hill a little way, still on the property but not adjacent to the RV. They were understanding about my newness to the business and gave me a good review, bless their hearts.

The second tenants never were able to make it up to the RV site. Their towing vehicle may or may not have had sufficient horsepower, but that did not matter as their trailer wallowed in the gravel and the towing vehicle’s rear wheels just spun ineffectually. I tried to refund their deposit, but my newness conspired to make me unable to figure out how to do so.

Friends and relatives also had trouble getting up my driveway, so I bit the bullet and paid $14,900 to have it paved with asphalt.

My third tenants (Evie & Harrison; via Airbnb) have now come and gone. They intended to stay for 28 days in a “skoolie” (refurbished retired school bus), accompanied by their minivan. I do not know how old the skoolie was or how well it had been maintained by previous owners, but it was long past “new.” These tenants drove here from Jacksonville, Florida. For the unaware, the Jacksonville School District is (was?) the only school district in the continental USA that does not own and operate its own school buses. Instead, the district’s buses are owned and operated by individuals, some driving their own buses and others hiring drivers, and the school board contracts with these owner-operators to ferry the kids around. Those buses are kept in service for many years, and their treatment and maintenance levels vary widely.

In the 1970s when I worked at a mountain summer camp for kids, Jacksonville school bus owner-operators were often hired to transport campers to local swimming holes, forest trails, and other attractions. I remember one owner-operators complaining to me that his bus had just blown its engine when being driven uphill on a mountain highway. He related that the bus was old, but thought it would have lasted another five years if it had been limited to flatlands.

When Evie & Harrison arrived, they were unable to back their skoolie into my RV site, so they opted to enter nose first. There were several reasons for that inability, IMO the most important being that their skoolie’s diesel engine was underpowered. It roared loudly as it inched slowly up the paved driveway and was loathe to move forward whenever the steering wheel was turned even slightly away from straight ahead. Another apparent issue was that the turnaround site had shrubby vegetation too close for easy radial steering, so I later used a chainsaw to cut the shrubs back another 6 to 8 ft. A third issue was that we were in the midst of a rainy spell, so the ungraveled ground at the edge of the site was soft. These three issues prevented the skoolie from maneuvering effectively during their 10-point turnings, and as a result the skoolie’s left front tire hit a soft spot and sank into the ground 6 to 8 inches. Because their skoolie had no way to be leveled as typical RVs do, this caused their floor to be slightly tilted in that position.

After being here a little over a week, they decided that the tilted floor was unacceptable. They tried to jockey the skoolie over to harder ground that was only about a yard away to the side, but the skoolie’s engine was unable to extricate the tire. Another issue with their skoolie, and presumably many other school buses, was that its rear axle had neither double-lockable wheels nor positraction, so gunning its engine when one rear tire was spinning on soft ground robbed power to the other wheel that was sitting (and unmoving) on solid ground. As a result, the bus went nowhere, so they gave up on this attempt and called a towing service.

Two days later, a mechanic driving a lifting-flatbed tow truck arrived to pull the skoolie out of the hole so that it could then be driven onto the firmer graveled ground. The mechanic had two ways he could do this. He could either use the truck’s power winch or pull the bus with a chain. He chose the latter. In his first attempt, he attached one end of his chain to the back of his tow truck and the other end to a steel hook welded to the back frame of the skoolie. This attempt ended suddenly when the chain’s end-hook popped off the bus hook. Harrison then re-hooked the chain and they gave it another go, slowly at first, and when that did not provide enough oomph, the mechanic powered up and suddenly soft-jerked the skoolie backward out of the tire-hole. Success! Or so we thought.

Harrison then drove the skoolie forward onto firm ground; however, the bus floor was still tilted. Evie told me the next day that the combination of the bus being tilted for the week and then winched out meant that the frame had been bent or other serious damage inflicted to the bus. They planned to have an insurance claim inspector diagnose it. There were two things wrong with Evie’s assertions: (1) vehicle frames as stoutly manufactured as school busses do not warp by sitting on uneven ground, and (2) the bus was "yanked" backward by the tow truck rather than being moved slowly by winching. Yanking a vehicle with a second vehicle is well-known to sometimes cause serious damage to one or both vehicles. Frankly, I am surprised the mechanic did not use the winch to pull the bus, as he confidently stated that the winch was capable of it. FWIW, I stood back and watched the operation; I did not lift an assisting hand due to red flags and liability concerns. The tenants elected to leave my site sooner than scheduled. I do not know if their plan was to move to a different RV site or to a garage to have the bus repaired.

Their effort to drive away three days later proved once again that their bus was underpowered for the mountains, as even on the asphalt driveway, the skoolie could not move forward even an inch when the front wheels were even slightly steered to the right or left. Also, with the shrubs now trimmed well away from the driveway, the skoolie still had turnaround issues, so they decided to back down the driveway to leave. Their original concern about being hemmed in by shrubbery was thus a third false claim.

As they prepared to leave, Evie informed me that the “damage” was to a shock absorber rather than to the bus frame. I do not know who made this determination, nor if it was even correct, as she had already made several false determinations. Relieved that their bus had not been seriously damaged, I agreed with her request for a pro rata refund, as they stayed for only 11 nights instead of the originally booked 28. Evie then said she would not give my site a review at all. I assumed she realized that their engine was underpowered for the mountains, their skoolie should have had leveling (and stabilizing) equipment, my shrubbery had nothing to do with their turnaround issues, flatlanders like themselves have a lot to learn about mountain living and driving, and they too wanted closure on this event. I therefore reciprocated the intention to give them no review either. We shook hands all around and they left.

However, any relief that I may have felt at that moment was dashed later that day upon learning that she had about-faced and submitted a review (her fourth false claim). I then learned that I cannot see her review until I give her one, kind of like buying a pig in a poke. At that point, my own angst rose to Code Orange. Evie’s unwarranted accusations that the soft ground had damaged their RV implied potentially thousands of dollars of liability, yet she offered no apology upon learning that she misspoke. Now she has given me a review that I cannot see, one that potentially adversely impacts my future income. This concern was aggravated by Airbnb rep “Jose,” who tried to get me to agree with something that Evie told Airbnb. Unfortunately, Jose’s Spanish accent was so strong that I had great difficulty understanding him, and had to ask him to repeat several things that he said. When I could not understand exactly what he was trying to get me to agree to that Evie claimed, I grew annoyed and instead put my own words into my mouth, after which he “agreed” with my wording.

Oh, by the way, Evie and Harrison released their pet cat to wander around outdoors unrestrained. My site profile states that all tenant pets must always be under positive control. I am a biologist who would rather have wildlife in my yard than someone else’ predatory pet.

I am now up in the air as to whether I want to continue to host an RV site at all. I am gestating on Evie’s misspeaking and failure to apologize, her telling me she was going to do one thing before asking for a partial refund and then doing something else after I agreed to the refund, they deliberately ignoring my pet control rule, Jose’s oft-incomprehensible English during communications regarding liability, Airbnb’s one-million-dollar “coverage” not actually being insurance, and my own uncertainty as to what requirements need to be placed on engine horsepower and RV and trailer maximum lengths. I think I will take my RV site off the market until I am back to Code Green and I know the maximum lengths of self-contained RVs and towing-towed combos for my site. In any case, NO MORE SKOOLIES!!!

This 10cm sally was spotted on the exterior of a solar greenhouse at 3400ft msl in Henderson Co., NC, in mid-October this year. iNaturalist identified it as a Blue Ridge Two-lined Salamander (Eurycea wilderae). Note the dorsolateral lines fading into spots halfway along the tail for its specific id. Note the fabulous yellow of the belly for your admiration!

iNaturalist graphs it as most commonly sighted in early October. It is otherwise a shy creature (and my first ever sighting), yet was obvious against the GH wall. iNaturalist was short on reproductive habitats, but did say that it lays eggs in late winter to early spring. Therefore, my guess is that it had come out for mating, and positioned itself well above the ground where its belly would attract attention. Presumably, it is male, but I really dunno.

Need Engineering Trade Journals

I am a member of AAAS, and while that organization’s Science News articles written by its journalism staff are long on who did the research and where they work, their articles are sadly short on the nitty gritty. Fortunately, AAAS also publishes the journal Science, which minutely details cutting-edge research applicable to multiple research disciplines. Good mag, that.

I love to read about science and engineering. Science indeed feeds the former, but not the latter. A long-ago workplace’s engineers used to pass around engineering trade magazines, which discussed details of the latest applications in engineering research. I read them as avidly as my engineering colleagues (I am a wildlife biologist). I miss those mags.

One article in particular, I believe in a magazine entitled Civil Engineering, was written by an engineer who immersed a “hardware cloth” wire grid into saltwater and applied a small current to it. Over a month-long period, a hard solid that looked like cement subsequently “grew” on the grid. He initially suspected it was a marine salt precipitate, but after turning off the power, it did not redissolve. He didn’t want to pay for a chemical assessment, but opined that the material might have been some kind of hydrated compound. Because (I think) he used raw saltwater, I wonder if there might also have been a microbial component. Whatever, thinking that it had potential as a building material, he patented it and dedicated the patent to the public. The popular press would never, ever do articles like that.

More recently, there have been a series of vapid articles in the pop press about a Netherlands architectural firm designing a floating town for Mauritius. Its goal is to stay ahead of global warming’s sea rise. The new town’s buildings will be on rafting platforms joined together and anchored in place within an atoll. The architectural drawings are all pretty faces, of course, but neither pop press articles nor company PR detail such things as what materials comprise the floats, platforms, infrastructure, and buildings. Yawn. How are individual floating pods interconnected? With steel cables? With wooden beams? How will they deal with fouling organisms that glom onto and weigh down the floats? Seascaping projects like this one fascinate me, but all the articles I’ve read about it so far (and I’ve looked hard!) are empty calories to my analytical mind.

Or how about Elon Musk’s fantasy about a Mars colony? What EXACTLY does he plan to do about the physiological impacts to the human body from long-term exposure to low gravity? There’s not a peep about that issue in pop press articles. Hellooo! Earth calling Mars!

So, I plan to spend a little time over the next few weeks looking at engineering and architectural trade mags to see if they might take me where I want to go, and at what cost. Do any of you engineers and architects out there have any pointers? TIA

 

My Florida Torrey 2020 Status

I am a Torreya Guardian, one of a dozen or so people who work to prevent the extinction of one of the most endangered conifers in the world. The Florida torrey, Torreya taxifolia, has an extremely restricted range that is located at the triple point where Florida, Georgia, and Alabama meet. Although it has protected habitat in Florida, especially within Torreya State Park and nearby conservancy preserves, it is there infested by a fungus (Fusarium torreyae) that kills nearly all torreys before they are mature enough to set seed. Connie Barlow reasoned that the best way to save the species was to assist in its migration to cooler climes where the fungus may not be able to survive. She and others collect seed annually for distribution to the rest of us. Hence, my plantings in the Blue Ridge Mountains of western North Carolina. So far, I have put 18 seedlings in the ground on my 2+ acres, 14 of which have survived to this day. The other four were killed by voles chewing through taproots blocking their way when digging their tunnels. This blog post documents the status of the remaining 14 as of today. The single torrey that was planted within the mature mixed forest here has grown the least, and now, nine years later, has grown to a height of only 13 inches:

The largest two were planted alongside my driveway where they get 4-5 hours of direct sunlight a day. Now, eight years later, they are 71 inches tall:

The others are intermediate in size according to the amount of insolation that they receive. Here's a couple of them:

Solar Greenhouse Thermal Mass Hydroponics

Many greenhouses today use thermal mass water tanks. The 26 ft diameter Open Spaces Growing Dome solar greenhouse that I manage for a friend at 3400 ft elevation in western North Carolina has one that might hold about 600 gallons. Climate zone maps say it is within zone 7, but I believe it might as well be zone 6 at that elevation. Whatever.

I have asked around on Facebook's greenhouse and general gardening groups whether anyone is using their thermal mass water tanks for hydroponic or aquaponic cultures, and have received zero responses one way or the other. My suspicion is that people who do so are doing it on a commercial scale, which is fine as far as that goes. However, there are many greenhouse gardeners who grow for their own and friends’ tables, so I think this represents a currently wasted opportunity. If you have a thermal mass water tank in your greenhouse, or are thinking about putting one in, consider adding edibles to those tanks. I don’t think you will find very much directly applicable information out there (and I could be wrong about that), but perhaps if we who do eat what comes out of our tanks, we can share what we have learned in Facebook greenhouse and gardening groups.

I started out by researching crops to grow on a small scale in the GH I manage. It turns out that there are few such crops, and many of them are invasive pests that can be illegal to grow; e.g., watercress (Nasturtium officinale), which grows rampantly in some of America’s natural streams. Other native wild species like yellow water lily (Nuphar advena) and wild rice (Zizania, four species) are too large and difficult to harvest from small water tanks. I uncovered no suitable aquatic plants, so I looked for wetland plants that might be grown on floats.

One of the most promising candidates is Chinese water chestnut (Eleocharis edulis). This is a small wetland plant that can be raised in shallow water in a matrix of organic mud (I don’t call it soil, as there is no such thing as a true wetland “soil”). I obtained ten corms of it from a nursery in Florida, then punched five half-inch holes in the bottom of a closed-cell foam packing tray and placed five corms in the holes equally spaced around in the tray:

I then added the other five corms and filled the tray with about two inches of organic mud. They took their sweet time to sprout and then grew relatively slowly, averaging maybe 14 inches in height by early July 2020 (week 13):

As of last week (week 31), some of the leaves had grown to a height of about 16 inches and had started to die back for the winter. I do not know if the original corms have budded new ones, as this is not obvious. They may have stored enough energy during this past growing season to add more corm/shoot growth in the coming spring, and I don’t want to retard that possibility by disturbing them now just prior to winter. About half of the mud is gone, presumably by decomposition, but possibly also by percolating down into the tank through the watering holes. I plan to add more mud during early springtime. In the photo, note the plants’ white roots floating just under the water’s surface:

There are a few small fish (unknown species) in the tank to keep mosquito larvae at bay. I was afraid the fish might eat the roots, but that does not seem to be a problem. There is a thick layer of algae growing atop the mud, and I wonder if it will adversely affect the plants, but that remains to be seen.

Despite the water chestnut’s slow growth, I was encouraged by the successful proof of concept, wherein the floating wetland bed remained afloat, the water chestnuts flourished, the mud acted as a wetland substrate, and nothing bad happened over the five-month experiment. However, further internet searches turned up no other suitably promising floating wet mud crops, so I turned my attention to drier floating substrates, and it being autumn becoming winter, settled on peas - specifically snow and sugar snap peas. I had already successfully raised those in outside beds nearby, so I knew they would work with the potting soil that was available.

This time, I used Styrofoam packaging material, again punched half-inch holes in the bottom for irrigation, and placed 1- to 2-inch rocks above the holes to elevate the potting soil above the water level and hopefully to keep most of the dirt from dropping through the holes. This is what it looked like one week after planting (late September 2020):

The pea seeds fairly leapt up out of the ground! Over the following weeks, the plants (vines) grew eight inches up and over the edge of the tank, another four feet down to the greenhouse floor, and then back up another two feet. That’s almost seven feet over 11 weeks, which was easily twice the length of pea vines grown outside in the garden bed during the summer. I don’t know if they grew faster in the greenhouse because peas are a cool season crop, but I also must admit that they have yet to flower and set seed. There could be a nutrient deficiency in the water tank, but that is hard to determine because water nutrient analyses are expensive and the county extension agency is oriented toward determining fertilizer levels in dirt, not water.

I like the idea of raising vines rather than bushes in the tank, because vines can grow over and down the sides of the tank whereas bushes (e.g., beans and tomatoes) could easily topple over if their substrates have no side support. I may try strawberries this coming spring.